High prevalence of substance use disorders among adolescents who use marijuana and inhalants

Drug and Alcohol Dependence 78 (2005) 23–32

High prevalence of substance use disorders among adolescents who use marijuana and inhalants Li-Tzy Wua,∗ , Daniel J. Pilowskyb , William E. Schlengera a

Center for Risk Behavior and Mental Health Research, RTI International, 3040 Cornwallis Road, Research Triangle Park, NC 27709-2194, USA b Mailman School of Public Health, Columbia University, 722 West 168th St., Room 1702, New York, NY 10032, USA Received 15 April 2004; received in revised form 18 August 2004; accepted 19 August 2004

Abstract Background: We examined the association between the use of inhalants, marijuana, and other drugs and recent DSM-IV substance use disorders among adolescents aged 12–17 years. Methods: Data were drawn from 2000 to 2001 National Household Surveys on Drug Abuse. Adolescents aged 12–17 years who reported having ever used an illicit drug in their lifetime were categorized into four mutually exclusive groups: inhalant users (16%), marijuana users (53%), inhalant and marijuana users (16%), and other drug users (15%). Logistic regression models were used to estimate associations with recent substance use diagnoses among lifetime adolescent drug users (N = 10,180). Results: We found that 31% of lifetime drug users reported having never used marijuana. One half of these atypical drug users were predominantly nonmedical users of pain relievers. Adolescents who used inhalants or other drugs but not marijuana were least likely to report multidrug use. Adolescents who reported using both inhalants and marijuana were most likely to use three or more classes of drugs (73%) and to receive a diagnosis of past year alcohol (35%) and drug (39%) abuse or dependence. Conclusions: Our study findings suggest that among lifetime adolescent drug users, those who use both inhalants and marijuana are at very high risk for alcohol and drug use disorders. © 2004 Elsevier Ireland Ltd. All rights reserved. Keywords: Adolescents; Alcohol use disorders; Drug use disorders; Inhalants; Marijuana

1. Introduction Youth marijuana and inhalant use is a subject of public health concern in both developed and developing countries (Kozel et al., 1995; Office of Applied Studies [OAS], 2002a). This study focuses on the use of marijuana, inhalants, and other drugs among adolescents in the United States and is based on a national survey of household residents supported by the U.S. Substance Abuse and Mental Health Services Administration (SAMHSA). We examine the likelihood of progression to substance use disorders among adolescents who used both marijuana and inhalants compared with those who used either drugs (i.e., marijuana users who did not ∗

Corresponding author. Tel.: +1 919 990 8463; fax: +1 919 485 5589. E-mail address: [email protected] (L.-T. Wu).

0376-8716/$ – see front matter © 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.drugalcdep.2004.08.025

use inhalants, inhalant users who did not use marijuana), and with those who used other drugs but no marijuana and inhalants. Marijuana is the illicit drug most commonly used in the United States and in most countries (Johnston et al., 2003; Office of Applied Studies [OAS], 2002a; Vega et al., 2002). Following marijuana, inhalants are the drugs most likely to be used by American adolescents (Johnston et al., 2003). Inhalant use also is a problem affecting adolescents of many other countries, particularly those living under disadvantaged conditions (De Micheli and Formigoni, 2004; Kozel et al., 1995; Pagare et al., 2004). Recent US national surveys indicate a dramatic increase in the number of new inhalant users from 0.6 million in 1994 to 1.2 million in 2000, and these new users are predominantly adolescents aged 12–17 years (OAS, 2003). The estimated

24

L.-T. Wu et al. / Drug and Alcohol Dependence 78 (2005) 23–32

number of new marijuana users in the U.S. was 2.5 million in 1994 and 3.0 million in 2000 (OAS, 2003). Although there is no consistent evidence of changes in the trend of firsttime marijuana use in the U.S. (OAS, 2003), there has been a considerable increase in marijuana treatment admissions, particularly among adolescents (OAS, 2001a). Marijuana use has been conceptualized as a gateway to other illicit drug use, and inhalant use has been viewed as a marker for multiple drug use. Several investigators have reported a general developmental sequence of substance use, from initial use of alcohol and/or cigarettes to marijuana, which then is followed by other drugs (Donnermeyer, 1993; Ellickson et al., 1992; Kandel et al., 1992; Yamaguchi and Kandel, 1984). Although a causal relationship between marijuana use and subsequent use of other drugs remains a subject of much discussion, the association between marijuana use and subsequent use of other illicit drugs has been well established empirically (Kandel, 2003; Lynskey et al., 2003). Inhalant use among adolescents is prevalent, but inhalants are the least studied among abused substances (Brouette and Anton, 2001; Kurtzman et al., 2001). Inhalant use may well be a second gateway to other illicit drug use (Novins et al., 2001). Like marijuana, the mean age of first use for inhalants is 13 years (Costello et al., 1999). Further, most inhalants are readily available in homes or offices and are legal to possess. Additionally, there are reports of a significant association between a history of inhalant use and the use of cocaine, heroin, and multiple drugs (Bennett et al., 2000; Dinwiddie et al., 1991; Johnson et al., 1995; Sch¨utz et al., 1994). Some research suggests that youthful inhalant use may be a marker for subsequent serious drug abuse, including injection drug use (Bennett et al., 2000; Dinwiddie et al., 1991; Johnson et al., 1995), which is more problematic than youthful marijuana use (Bennett et al., 2000). Many inhalant users also use other drugs, especially marijuana (Bennett et al., 2000; Howard and Jenson, 1999). Studies of either marijuana or inhalants typically do not consider that many adolescents use both drugs. In this study, we sought to understand better the association between the history of marijuana and inhalant use and recent substance use disorders. By disaggregating the history of drug use into inhalant use, marijuana use, inhalant and marijuana use, and other illicit drug use, we examined the strength of each association with recent alcohol and drug use disorders. We hypothesized that lifetime marijuana and inhalant use would be associated with past year alcohol and drug use disorders and that this association would be stronger when both drugs were used. Their use may be associated with the use of other illicit drugs, as well as substance abuse and dependence. Using advanced statistical procedures to adjust for demographic variations while estimating the associations of interest, we examined several potential antecedents and correlates of substance use disorders: multidrug use, history of foster care placement, history of incarceration, delin-

quency and conduct problems, mental health service utilization, and age at first use of alcohol, inhalants, and marijuana (Grant and Dawson, 1998; Grant et al., 2001; Wu et al., 2004).

2. Method 2.1. Data source This study is based on data from the public use files of the 2000 and 2001 National Household Survey on Drug Abuse (NHSDA). The NHSDA represents a major effort to provide population estimates of substance use and its correlates in the U.S. population (OAS, 2001b, 2002a). It utilizes multistage area probability sampling methods to select a representative sample of the US civilian, noninstitutionalized population aged 12 years or older for participation in the study. The sample includes residents of shelters, rooming houses, dormitories, and group homes; residents of Alaska and Hawaii; and civilians residing on military bases. Homeless persons who did not use shelters, active military personnel, and residents of institutional group quarters (jails and hospitals) are not covered by the survey (OAS, 2001b). NHSDA participants were interviewed in private at their place of residence. The 2000–2001 surveys utilized a computer-assisted interviewing (CAI) methodology to increase the level of honest reporting of illicit drug use behaviors. The CAI methodology includes a combination of computer-assisted personal interviewing (CAPI) and audio computer-assisted self-interviewing (ACASI) methodologies. ACASI interviewing was used for questions of a sensitive nature (e.g., substance use). Respondents read the questions on the computer screen or the questions were read to the respondents through headphones, and they entered their responses directly into the computer. In the 2000 and 2001 surveys, a total of approximately 70,000 respondents aged 12 years or older completed the interview annually. The weighted response rate for adolescents aged 12–17 years was consistently over 80% (OAS, 2002b). Each independent, cross-sectional NHSDA sample was representative of the US general population aged 12 years or older. NHSDA design and data collection procedures have been reported in detail elsewhere (OAS, 2001b, 2002a). 2.2. Study sample This study was declared exempt from the RTI International Institutional Review Board because it used an existing public use data file. No information or identifiers on the data file can be associated with any individual survey respondent. Secondary data analyses were conducted on adolescent respondents aged 12–17 years (N = 36,859). There were few differences in the distribution of age, gender, race/ethnicity, family income, and population density across the two survey

L.-T. Wu et al. / Drug and Alcohol Dependence 78 (2005) 23–32

respondents. In this combined sample of adolescents aged 12–17 years, 49% were females, 33% were aged 12 or 13 years, 35% were members of nonwhite minority groups, 43% reported an annual family income of $40,000 or less, and 23% resided in nonmetropolitan areas. 2.3. Study variables 2.3.1. Drug use variables The NHSDA assessments of alcohol and drug use included a detailed verbal description of each drug group and lists of qualifying drugs, including a colored pill card with pictures of different pharmaceutical products. For alcohol and each drug class, respondents were asked about their use, recency of use, and age of first use. We used lifetime inhalant and marijuana use variables to categorize all lifetime drug users (N = 10,180) into four mutually exclusive subgroups. They included (1) inhalant users (16%, lifetime inhalant users who had never used marijuana, regardless of other drug use), (2) marijuana users (53%, lifetime marijuana users who had never used inhalants, regardless of other drug use), (3) inhalant and marijuana users (16%, adolescents who had ever used any inhalant and marijuana, regardless of other drug use), and (4) other drug users (15%, lifetime drug users who had never used inhalants and marijuana). Other drug use included any use of cocaine/crack, heroin, hallucinogens, or nonmedical use of sedatives, tranquilizers, pain relievers, and stimulants. 2.3.2. Past year substance abuse or dependence The 2000–2001 NHSDA (OAS, 2001b, 2002a) included a series of standardized questions to assess alcohol and drug dependence in the year prior to the interview based on seven criteria specified by the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (American Psychiatric Association [APA], 1994). These assessments were patterned after the questions used in the National Comorbidity Survey (NCS) (Kessler et al., 1994) and were revised to meet the DSM-IV criteria. They included (1) tolerance, (2) withdrawal, (3) inability to cut down or stop substance use, (4) spending a great deal of time getting or using the substance or getting over its effects, (5) reducing or giving up important activities because of substance use, (6) using the substance more often than intended, and (7) continuing substance use despite substance use-related health or psychological problems. These questions were asked separately for alcohol and each of nine drug classes (i.e., inhalants, marijuana, cocaine/crack, heroin, hallucinogens, and nonmedical use of sedatives, tranquilizers, pain relievers, and stimulants). Alcohol dependence referred to the presence of at least three dependence criteria for alcohol in the prior year. Drug dependence referred to the presence of at least three dependence criteria for a specific drug class in the prior year. Four DSM-IV (APA, 1994) abuse criteria for alcohol and each drug class also were assessed with standardized items: (1) recurrent substance use resulting in serious problems at

25

home, work, or school, (2) recurrent substance use in situations that put the person in physical danger, (3) recurrent substance-related legal problems, and (4) continuing substance use despite having social or interpersonal problems caused by substance use. For both alcohol and drug classes, adolescents who met at least one abuse criterion for a specified substance and who did not meet criteria for dependence on that specified substance were classified as abuse. In this paper, drug abuse or dependence was defined as abuse of or dependence on any one of the nine drug classes specified above. 2.3.3. Correlates of past year substance abuse or dependence We also examined the following potential antecedents and correlates of recent substance abuse or dependence: history of incarceration, history of foster care placement, delinquent behaviors or conduct problems, mental health service utilization, history of multidrug use, and age at first use of alcohol, inhalants, and marijuana. The following demographic variables also were considered: age, gender, race/ethnicity, total family income, and population density. The NHSDA classified population density into large metropolitan (areas with a population ≥1 million), small metropolitan (areas with a population < 1 million), and nonmetropolitan areas (outside a metropolitan statistical area). Adolescents who responded affirmatively to “have you ever been in foster care?” and to “have you ever been in a jail or a detention center” were considered to have a history of foster care placement and incarceration, respectively. The following past year delinquency or conduct problems were assessed: (1) getting into a serious fight at school or work, (2) taking part in a group fight against another group, (3) carrying a handgun, (4) selling illicit drugs, (5) stealing anything worth more than US$ 50, and (6) attacking someone with the intent to seriously hurt him or her. These six types of delinquent behaviors or conduct problems were grouped into three categories (none, 1–2, and 3 or more). Mental health service utilization was defined as any use of treatment or counseling at any service location in the prior year for emotional or behavioral problems other than alcoholor drug-related problems (e.g., hospital, private doctor’s office, mental health clinic or program, general medical setting, or school). The number of lifetime drugs used (cocaine/crack, inhalants, marijuana/hashish, heroin, hallucinogens, sedatives, tranquilizers, pain relievers, and stimulants) was summed and grouped into three categories (1–2, 3, and 4 or more drug classes). Age at first use of alcohol, inhalants, or marijuana was categorized into two groups: before 13 years and 13 years or older (including no use). For each substance, because of a very small number of nonusers reporting any substance abuse or dependence (the outcome variable), nonusers were included in the later onset group (aged 13 years or older). Because we focused on alcohol and illicit drugs, tobacco use was not examined in this study.

26

L.-T. Wu et al. / Drug and Alcohol Dependence 78 (2005) 23–32

2.4. Data analysis

We report odds ratios (ORs) to estimate the strength of an association.

Data were weighted to reflect the representativeness of the NHSDA sample and were analyzed by SUDAAN software (Research Triangle Institute, 2002), which applies a Taylor series linearization method to account for the effects of the complex NHSDA design features (e.g., weighting). All percentages reported in this paper are weighted estimates, while sample sizes are unweighted. We first examined the prevalence of lifetime use of inhalants, marijuana/hashish, and other drugs among all adolescents aged 12–17 years. We then explored the pattern of substance use, abuse, and dependence by history of inhalant and marijuana use among the subsample of adolescents who reported the use of any drug in their lifetime. To hold constant variations in demographics, multiple logistic regression procedures (Hosmer and Lemeshow, 2000) were conducted to identify correlates of recent alcohol and drug use disorders, respectively, among all lifetime drug users.

3. Results 3.1. Use of marijuana, inhalants, and other drugs among adolescents The prevalence of lifetime drug use by demographic characteristics is summarized in Table 1. Among adolescents aged 12–17 years (N = 36,859), 9% reported any lifetime use of inhalants and 19% reported any lifetime use of marijuana. The prevalence of lifetime use for inhalants (without marijuana), marijuana (without inhalants), inhalants and marijuana, and other drugs was 4, 15, 4, and 4%, respectively. This pattern was consistent across the two survey years. The prevalence of any inhalant use and any marijuana use peaked at the same age: 11 and 24% of adolescents 15 years

Table 1 Prevalence of lifetime drug use among adolescents aged 12–17 years (N = 36,859) Any inhalants

Any marijuana

Inhalants without marijuanaa

Marijuana without inhalantsa

8.8

18.9

4.4

14.6

4.4

4.2

4.9* 7.6 9.7 10.5 9.9 9.7

2.2* 5.6 12.5 23.6 17.0 15.8

4.1* 5.9 6.2 4.7 3.2 1.9

1.4* 3.9 9.0 17.8 24.6 30.9

0.8* 1.7 3.5 5.8 6.7 7.8

3.1* 3.9 4.2 4.9 4.7 4.5

8.7 8.8

19.8* 18.0

4.3 4.5

15.4* 13.7

4.4 4.4

3.8* 4.7

Race/ethnicityb White African American Hispanic American Indian Asian More than one race

9.5* 5.3 9.0 13.2 6.5 11.2

19.9* 15.3 19.3 45.2 8.9 22.2

4.4 4.1 4.4 2.8 4.6 5.3

14.8* 14.1 14.7 34.7 7.0 16.3

5.1* 1.2 4.5 10.4 1.9 5.8

3.8* 5.9 4.3 5.5 5.4 4.5

Family income US$ 0–19,999 US$ 20,000–39,999 US$ 40,000–74,999 US$ 75,000 or more

8.1 9.1 9.1 8.4

19.9* 20.3 18.3 17.7

3.7 4.5 4.6 4.4

15.5* 15.8 13.8 13.7

4.4 4.5 4.5 4.0

5.0 4.8 4.0 3.4

7.9* 8.9 10.1

17.7* 20.2 19.4

4.3 4.2 4.8

14.0 15.6 14.1

3.7* 4.6 5.3

4.3 3.9 4.6

8.8 8.7

18.2 19.7

4.4 4.3

13.8 15.3

4.4 4.4

4.2 4.2

Overall (%) Age 12 13 14 15 16 17 Gender Male Female

Population density Large metro Small metro Nonmetro Survey year 2000 2001 ∗ a b

Chi square test, p < 0.001, for that drug use group and the corresponding demographic variable. Regardless of the use of other drugs. American Indian includes Alaska natives. Asian includes Asians, native Hawaiians, and other Pacific islanders.

Inhalants and marijuanaa

Other drugs only

L.-T. Wu et al. / Drug and Alcohol Dependence 78 (2005) 23–32

of age used inhalants and marijuana, respectively. However, the prevalence of inhalant use without marijuana peaked at 13–14 years of age (6%), while the prevalence of marijuana use without inhalants increased with age and peaked at 17 years of age (31%). The use of other drugs ranged from 3% at age 12 to 5% at age 15 or older. American Indians or Alaska Natives reported the highest prevalence of any marijuana use (45%), with (10%) or without (35%) using inhalants. There was little demographic variation in the use of inhalants or of other drugs. 3.2. Substance use among drug users Table 2 displays the prevalence of alcohol and drug use among adolescents who reported any use of a drug in their lifetime (N = 10,180). Among this subsample of lifetime drug users, marijuana users who also used inhalants reported the highest prevalence of lifetime use of alcohol (97%), cocaine/crack (27%), heroin (5%), hallucinogens (49%), sedatives (8%), stimulants (33%), and tranquilizers (25%). With

27

the exception of alcohol, prevalence rates of these substances were much lower in the remaining three groups (inhalants only, marijuana only, and other drugs only). The prevalence of alcohol use was almost as high in the marijuana only group (91%) and remained relatively high in the other two groups (55–60%). In contrast, users of other illicit drugs (those who had never used inhalants and marijuana) reported a higher prevalence of pain reliever use (77%) than the remaining three groups. They also reported a higher prevalence of prescription-type drug use (sedatives, stimulants, and tranquilizers) than those who used either inhalants or marijuana, but not both. 3.3. Alcohol and drug use disorders among drug users Prevalence rates of past year substance use disorders among lifetime and past year drug users are summarized in Table 3. Among lifetime drug users, the prevalence of past year alcohol and drug abuse and dependence was highest among adolescents who reported using both marijuana and

Table 2 Substance use characteristics among adolescent drug users (N = 10,180) Inhalants without marijuanaa

Marijuana without inhalantsa

Inhalants and marijuanaa

Other drugs only

t-test or χ2 (d.f.) P-values

Sample size Mean age of first inhalant use (SE) Mean age of first marijuana use (SE) Mean number of drugs ever used (SE)

n = 1677 11.8 (0.07) – 1.4 (0.02)

n = 5331 – 13.8 (0.03) 1.7 (0.02)

n = 1655 13.2 (0.07) 13.0 (0.06) 3.9 (0.05)

n = 1517 – – 1.2 (0.01)

t-test (<0.001) t-test (<0.001) t-test (<0.001)

Number of drugs ever used 1–2 3 4 or more

91.4 5.6 3.0

84.1 8.9 7.0

26.6 24.2 49.2

97.8 1.6 0.6

Number of drugs ever used 1 2 3 4 or more

73.4 18.0 5.6 3.0

63.0 21.1 8.9 7.0

0.0 26.6 24.2 49.2

87.6 10.2 1.6 0.6

Age of first alcohol use 12 or younger 13 or older No use

30.6 29.6 39.8

27.8 63.4 8.8

48.0 48.5 3.5

21.9 33.5 44.6

Age of first inhalants 12 or younger 13 or older

60.8 39.2

–

32.0 68.0

–

179.0 (1) <0.001

Age of first marijuana 12 or younger 13 or older

–

20.9 79.1

36.5 63.5

–

83.9 (1) <0.001

Ever used alcohol Ever used cocaine/crack Ever used heroin Ever used hallucinogens Ever used pain relievers Ever used sedatives Ever used stimulants Ever used tranquilizers

60.2 0.6 0.1 5.0 18.3 2.8 8.4 4.1

91.2 7.4 0.7 20.6 18.7 1.0 9.6 6.6

96.6 26.5 5.3 48.6 48.1 7.7 32.9 24.9

55.4 1.4 0.2 9.8 76.6 3.8 15.6 7.9

799.6 (3) <0.001 362.9 (3) <0.001 80.3 (3) <0.001 489.3 (3) <0.001 991.1 (3) <0.001 103.9 (3) <0.001 241.1 (3) <0.001 189.2(3) <0.001

a

Regardless of the use of other drugs.

931.5 (6) <0.001

1353.5 (9) <0.001

927.6 (6) <0.001

28

L.-T. Wu et al. / Drug and Alcohol Dependence 78 (2005) 23–32

Table 3 Prevalence of past year alcohol and drug use disorders among lifetime and past year drug users Prevalence of abuse or dependence

Sample size Alcohol Any drug Inhalants Marijuana Cocaine Heroin Hallucinogens Pain relievers Sedatives Stimulants Tranquilizers a

Lifetime drug users (N = 10,180)

Past year drug users (N = 7215)

Inhalants without marijuanaa

Marijuana without inhalantsa

Inhalants and marijuanaa

Other drugs only

Inhalants without marijuanaa

Marijuana without inhalantsa

Inhalants and marijuanaa

Other drugs only

1677 6.0 6.0 3.2 – 0.1 0 1.1 2.0 0.3 0.8 0.4

5331 16.8 16.0 – 14.4 0.7 0.2 1.5 1.3 0.2 0.6 0.4

1655 35.0 38.9 5.3 31.7 4.4 1.2 7.8 6.3 0.7 3.7 2.6

1517 6.2 7.0 – – 0.1 0 0.7 5.1 0.3 1.2 0.5

671 10.9 12.2 8.4 – 0 0 2.8 2.5 0.3 1.5 1.1

4605 22.2 24.3 – 22.1 1.5 0.3 2.6 2.1 0.2 1.0 0.7

642 43.0 51.1 13.0 42.0 5.1 2.4 12.2 9.5 1.1 5.0 4.9

1297 9.5 13.1 – – 0.9 0 1.7 8.3 0.9 2.5 0.6

Regardless of the use of other drugs.

inhalants (35% for alcohol, 39% for any drug), followed by those who used marijuana but had not used inhalants (17% for alcohol, 16% for any drug). There were no significant differences in substance abuse and dependence among those who used inhalants but had not used marijuana and those who used only other drugs (6–7%). Among past year drug users (N = 7215), a consistent and even higher prevalence of abuse and dependence was observed among adolescent drug users who reported using both marijuana and inhalants: 43 and 51% met the criteria for alcohol and drug abuse or dependence, respectively. Corresponding prevalence rates were 22 and 24% for users of marijuana only, 11 and 12% for users of inhalants only, and 10 and 13% for users of other drugs. 3.4. Odds ratios of past year alcohol abuse or dependence among lifetime drug users The results of logistic regression analyses of past year alcohol and drug use disorders in relation to a history of inhalant and marijuana use and other suspected correlates are shown in Table 4. Among lifetime drug users, adolescents reporting a history of using both marijuana and inhalants were three times as likely as those using inhalants but no marijuana to meet criteria for past year alcohol abuse or dependence (adjusted odds ratio [AOR] = 3.0, 95% confidence interval [CI] = 2.1–4.2). Adolescents who used marijuana but had not used inhalants were twice as likely as inhalant users who had not used marijuana to receive a diagnosis of alcohol abuse or dependence (AOR = 2.3, 95% CI = 1.7–3.2). Other drug users were not different from inhalant users who had not used marijuana in the prevalence of alcohol abuse or dependence. Among these lifetime drug users, older age, female gender, highest level of family income, residing in nonmetropolitan areas, recent mental health service utilization, a history of incarceration, delinquent behaviors, a history of multidrug

use, and onset of alcohol use before age of 13 were associated with increased odds of recent alcohol abuse or dependence. Whites, Hispanics, American Indians, and Alaska Natives were about twice as likely as African Americans to meet the criteria for alcohol abuse or dependence. 3.5. Odds ratios of past year drug abuse or dependence among lifetime drug users As shown in Table 4, associations between a history of marijuana or inhalant use and past year drug abuse or dependence followed a similar pattern. Adolescent drug users who used both marijuana and inhalants (AOR = 3.0, 95% CI = 2.1–4.2) and those who used marijuana but no inhalants (AOR = 2.5, 95% CI = 1.8–3.4) were about three times as likely as those using inhalants but no marijuana to meet criteria for drug abuse or dependence. Other drug users were slightly more likely than inhalant users who did not use marijuana to meet the criteria for drug abuse or dependence (AOR = 1.5, 95% CI = 1.0–2.1). Past year utilization of mental health services, a history of incarceration, delinquent behaviors, and a history of multidrug use also were associated with increased odds of drug abuse or dependence. Asians were twice as likely as African Americans to receive a diagnosis of drug abuse or dependence. However, gender, family income, population density, age of first inhalant use, and age of first alcohol use were not associated with drug abuse or dependence, while onset of marijuana use before age of 13 was a significant correlate.

4. Discussion The most salient finding was the strikingly high prevalence of alcohol and drug use disorders (35 and 39%, respectively) among adolescent drug users who reported using both marijuana and inhalants in their lifetime as compared with those

L.-T. Wu et al. / Drug and Alcohol Dependence 78 (2005) 23–32

29

Table 4 Odds ratios (ORs) and 95% confidence interval (CI) of past year substance abuse or dependence among lifetime adolescent drug users aged 12–17 years, by inhalant and marijuana use status (N = 10,180) Logistic regression model

Alcohol abuse or dependence

Drug abuse or dependence

Unadjusted OR (95% CI)

Adjustedd

Unadjusted OR (95% CI)

Adjustedd OR (95% CI)

Lifetime inhalants or marijuana use Marijuana vs. inhalants Inhalants and marijuana vs. inhalants Other drugs vs. inhalants

3.2 (2.5–4.1)c 8.5 (6.4–11.2)c 1.0 (0.7–1.5)

2.3 (1.7–3.2)c 3.0 (2.1–4.2)c 1.1 (0.7–1.6)

3.0 (2.3–3.9)c 10.0 (7.7–13.1)c 1.2 (0.9–1.6)

2.5 (1.8–3.4)c 3.0 (2.1–4.2)c 1.5 (1.0–2.1)a

Age in years 14–15 vs. 12–13 16–17 vs. 12–13

2.6 (2.0–3.4)c 3.5 (2.8–4.5)c

2.0 (1.5–2.7)c 2.7 (2.0–3.6)c

1.8 (1.4–2.2)c 1.9 (1.6–2.3)c

1.3 (1.0–1.7)a 1.3 (1.0–1.7)a

Gender Male vs. female

0.9 (0.8–1.1)

0.8 (0.7–0.9)c

1.0 (0.9–1.2)

0.9 (0.8–1.0)

Race/ethnicitye White vs. African American Hispanic vs. African American American Indian vs. African American Asian vs. African American More one race vs. African American

2.4 (1.9–3.1)c 2.1 (1.5–2.8)c 3.3 (1.9–5.7)c 1.9 (1.1–3.2)a 2.0 (1.1–3.4)a

1.6 (1.2–2.1)c 1.6 (1.2–2.3)b 2.5 (1.4–4.6)b 1.9 (1.0–3.6) 1.2 (0.7–2.0)

1.4 (1.2–1.7)c 1.5 (1.1–1.9)b 1.9 (1.1–3.4)a 1.7 (1.0–2.7)b 1.4 (0.9–2.3)

0.9 (0.7–1.1) 1.0 (0.8–1.4) 1.1 (0.6–2.2) 1.7 (1.0–2.7)a 0.8 (0.5–1.3)

Family income US$ 0–19,999 vs. US$ 75K+ US$ 20 K–39,999 vs. US$ 75 K+ US$ 40 K–74,999 vs. US$ 75 K+

0.8 (0.7–1.0) 0.8 (0.7–1.0)a 1.1 (0.9–1.2)

0.7 (0.6–0.9)b 0.7 (0.6–0.8)c 1.0 (0.9–1.2)

1.0 (0.8–1.3) 1.1 (0.9–1.3) 1.0 (0.9–1.2)

0.8 (0.6–1.0) 1.0 (0.8–1.2) 1.0 (0.8–1.2)

Population density Large metro vs. nonmetro Small metro vs. nonmetro

0.7 (0.7–0.9)c 0.8 (0.7–0.9)b

0.8 (0.6–0.9)b 0.7 (0.6–0.9)c

1.0 (0.9–1.2) 1.1 (0.9–1.3)

1.1 (0.9–1.3) 1.0 (0.9–1.3)

1.6 (1.4–1.8)c

1.2 (1.0–1.4)a

2.1 (1.9–2.4)c

1.6 (1.4–1.9)c

2.1 (1.8–2.6)c

1.3 (1.0–1.6)a

2.9 (2.4–3.5)c

1.4 (1.2–1.7)c

1.6 (1.2–2.1)c

1.2 (0.9–1.7)

2.1 (1.7–2.7)c

1.3 (1.0–1.8)

Number of delinquent behaviors 1–2 vs. none ≥3 vs. none

2.0 (1.7–2.3)c 4.9 (4.1–5.9)c

1.9 (1.6–2.3)c 3.6 (2.9–4.5)c

2.3 (2.0–2.7)c 6.1 (5.2–7.3)c

2.0 (1.7–2.3)c 3.3 (2.7–4.1)c

Number of lifetime drugs used 3 vs. 1– 2 drugs ≥ 4 vs. 1– 2 drugs

3.0 (2.5–3.6)c 6.0 (5.1–7.0)c

1.7 (1.4–2.1)c 2.5 (2.0–3.0)c

4.1 (3.4–4.9)c 9.4 (8.0–11.1)c

2.8 (2.2–3.4)c 5.0 (4.0–6.2)c

Age of first alcohol use ≤12 vs. ≥13 years and no use

1.9 (1.7–2.2)c

1.6 (1.3–1.8)c

1.7 (1.5–1.9)c

0.9 (0.8–1.1)

Age of first inhalant use ≤12 vs. ≥13 years and no use

0.8 (0.7–1.0)

0.9 (0.7–1.2)

1.1 (0.9–1.3)

1.0 (0.8–1.3)

Age of first marijuana use ≤12 vs. ≥13 years and no use

1.9 (1.7–2.2)c

0.9 (0.8–1.1)

2.8 (2.4–3.3)c

1.4 (1.2–1.7)c

Survey year 2000 vs. 2001

1.0 (0.9–1.1)

1.0 (0.9–1.2)

1.0 (0.8–1.1)

1.0 (0.8–1.1)

Mental health service utilization Yes vs. no History of incarceration Yes vs. no History of foster care placement Yes vs. no

a b c d e

OR (95% CI)

P ≤ 0.05. P ≤ 0.01. P ≤ 0.001. Each logistic regression model includes all variables specified in that column. American Indian includes Alaska Natives. Asian includes Asians, Native Hawaiians, and other Pacific Islanders.

who reported using either inhalants (6 and 6%) or marijuana (17 and 16%) and those who reported using other drugs (6 and 7%). This pattern was found when the analysis was based on all adolescents who reported lifetime drug use, and it was even more pronounced when the analysis was restricted to

past year drug users. In the latter group, 43 and 51% met the criteria for alcohol and drug use disorder, respectively. These adolescents, who constitute 16% of all lifetime drug users, also were most likely to use three or more classes of drugs (73%).

30

L.-T. Wu et al. / Drug and Alcohol Dependence 78 (2005) 23–32

Clearly, marijuana users who also use inhalants are the group with the highest prevalence of alcohol and drug use disorders. Early marijuana use and early inhalant use are each associated with substance abuse and with the use of cocaine, heroin, and other drugs (Dinwiddie et al., 1991; Ellickson and Morton, 1999; Gfroerer et al., 2002; Johnson et al., 1995; Sch¨utz et al., 1994). Our findings further reveal that use of both marijuana and inhalants may be a marker for serious drug abuse or dependence, even after the influences of demographic characteristics, history of multidrug use, and other suspected determinants of drug abuse and dependence are held constant. Adolescents reporting lifetime use of marijuana but no inhalants had a much higher prevalence of alcohol and drug use disorders than those who used only inhalants and those who used other drugs. These estimates of substance use disorders represent the most recent findings for American adolescents in the general population. Our findings also indicate that inhalant use is more prevalent than the use of marijuana or other drugs among young adolescents aged 12–13 years, and the mean age at first inhalant use tends to be earlier than first marijuana use. The gateway theory suggests that marijuana use typically precedes the use of other drugs (Kandel et al., 1992; Yamaguchi and Kandel, 1984). In this nationally representative sample of adolescents aged 12–17 years, we found that 31% of lifetime drug users reported having never used marijuana. One half of these atypical drug users were predominantly nonmedical users of pain relievers (77% used a pain reliever). The remaining atypical drug users used inhalants, and 27% of these inhalant users also used other drugs. Atypical drug users were the least likely to report multidrug use. This study shows that a history of inhalant use is not necessarily associated with the use of cocaine, heroin, or multiple drugs as suggested in several studies (Bennett et al., 2000; Dinwiddie et al., 1991; Johnson et al., 1995; Sch¨utz et al., 1994). In this sample, one half of lifetime inhalant users reported no marijuana use, and less than 1% of inhalant users (without using marijuana) used cocaine or heroin. This finding should be viewed cautiously, however, because inhalant users who do not use marijuana are probably younger than those who also use marijuana and may not have reached the age when adolescents start using other drugs (e.g., cocaine and heroin). Our findings suggest that adolescent drug users aged 12–17 years who reported never having used marijuana, inhalants, or both may be different from those with a lifetime history of using one or both drugs. As shown in Table 2, they have a very different pattern of drug use. Their lifetime prevalence of the use of pain relievers is much higher (77%) than that reported by adolescents using inhalants, marijuana, or both. Prescription-type drugs are their main drugs of choices, and they are least likely to use multiple drugs. These findings are limited by the cross-sectional nature of the NHSDA design and the reliance on self-reported drug use. Although adolescent self-reports of drug use are generally considered valid and reliable, underreporting of drug use

is likely to occur in a household setting (Harrison et al., 1993; Gfroerer et al., 1997; Needle et al., 1983; Winters et al., 1990, 1991). Individuals who report using multiple drugs and those who report symptoms of a drug use disorder appear to be more likely to disclose their drug use behaviors (Colon et al., 2002). It is noteworthy that the NHSDA methodology has produced more valid results than a telephone interview (Turner et al., 1992), and the use of computer-assisted survey technology has been found to increase adolescents’ self-reports of drug use and the other risky behaviors (Turner et al., 1998). Investigators also have found that lifetime prevalence rates of alcohol and drug use in the 1991 NHSDA are consistent with the NCS estimates conducted in 1990–1992 (Anthony et al., 1994). Second, our assessments of alcohol and drug use diagnoses are based on a single structured interview administrated by trained nonclinicians, and these diagnoses are not validated by clinicians. Nonetheless, Kandel and co-workers (1997) examined the prevalence of past year alcohol and drug dependence measured in the 1991–1993 NHSDA and found that dependence rates in the NHSDA were generally similar to the rates from the NCS and the National Longitudinal Alcohol Epidemiologic Survey (NLAES). Population estimates of substance use disorders conducted by a survey as large and geographically dispersed as the NHSDA require the use of sophisticated survey research methods. Such large epidemiological studies do not provide the same context for studies of reliability and validity as studies with smaller samples, where there might be multiple opportunities for repeated assessments and detailed diagnostic cross-examinations (Wagner and Anthony, 2002). Limitations of such large-scale epidemiological studies have been discussed in detail elsewhere (Anthony et al., 1994; Kessler et al., 1994; Wagner and Anthony, 2002). Last, a small but high-risk group of drug users (e.g., incarcerated and homeless adolescents; less than 2% of the U.S. population) was not included in the NHSDA, and therefore, our findings may not apply to them. Nonetheless, population estimates are not likely to be affected. It has been shown that the inclusion of institutionalized and homeless individuals in large-scale surveys does not change substantially the overall population estimates of drug dependence because of the small number of individuals in these subgroups relative to the large size of the U.S. household population (Anthony and Helzer, 1991). Despite these limitations, our findings have important implications for researchers and clinicians. This study is based on a nationally representative sample of adolescents recruited using a sophisticated survey methodology. We found a surprisingly high prevalence of DSM-IV alcohol and drug use disorders among adolescents who reported a lifetime history of using both inhalants and marijuana. This may well be a new high-risk group, deserving more attention from investigators. Progression to substance abuse or dependence is associated with utilization of mental health services, a history of incarceration, delinquent behaviors, and multidrug use. Clinicians

L.-T. Wu et al. / Drug and Alcohol Dependence 78 (2005) 23–32

should be aware of the existence of this high-risk group because they may be in the best position to identify these very high-risk young drug users and refer them for drug counseling or treatment in a specialized setting (American Academy of Pediatrics, 1998; Klein and Wilson, 2002). Given that more than one million Americans become new inhalant users annually (OAS, 2003) and that inhalants are the only drug showing clear evidence of increasing use among American adolescents in 2003 (Johnston et al., 2004), there is a need to continue identifying and developing effective prevention strategies to reduce marijuana and inhalant use (e.g., Griffin et al., 2003; Palmgreen et al., 2001).

Acknowledgments This work was supported by the National Institute on Drug Abuse (R21DA015938). The Substance Abuse and Mental Health Data Archive (SAMHDA) and the Inter-University Consortium for Political and Social Research (ICPSR) provided the public use data files of the National Household Survey on Drug Abuse.

References American Academy of Pediatrics, 1998. Tobacco, alcohol, and other drugs: the role of the pediatrician in prevention and management of substance abuse. Pediatrics 101, 125–128. American Psychiatric Association, 1994. Diagnostic and Statistical Manual of Mental Disorders. American Psychiatric Association, Washington DC. Anthony, J.C., Helzer, J.E., 1991. Syndromes of drug abuse and dependence. In: Robins, L.N., Regier, D.A. (Eds.), Psychiatric disorders in America: The Epidemiologic Catchment Area Study. The Free Press, New York, pp. 116–154. Anthony, J.C., Warner, L.A., Kessler, R.C., 1994. Comparative epidemiology of dependence on tobacco, alcohol, controlled substances, and inhalants: basic findings from the National Comorbidity Survey. Exp. Clin. Psychopharmacol. 2, 244–268. Bennett, M.E., Walters, S.T., Miller, J.H., Woodall, W.G., 2000. Relationship of early inhalant use to substance use in college students. J. Subst. Abuse 12, 227–240. Brouette, T., Anton, R., 2001. Clinical review of inhalants. Am. J. Addict. 10, 79–94. Colon, H.M., Robles, R.R., Sahai, H., 2002. The validity of drug use selfreports among hard core drug users in a household survey in Puerto Rico: comparison of survey responses of cocaine and heroin use with hair tests. Drug Alcohol Depend. 67, 269–279. Costello, E.J., Erkanli, A., Federman, E., Angold, A., 1999. Development of psychiatric comorbidity with substance abuse in adolescents: effects of timing and sex. J. Clin. Child Psychol. 28, 298–311. De Micheli, D., Formigoni, M.L., 2004. Drug use by Brazilian students: associations with family, psychosocial, health, demographic, and behavioral characteristics. Addiction 99, 570–578. Dinwiddie, S.H., Reich, T., Cloninger, C.R., 1991. Solvent use as a precursor to intravenous drug abuse. Compr. Psychiatry 32, 133–140. Donnermeyer, J.F., 1993. Rural youth usage of alcohol, marijuana, and “hard” drugs. Int. J. Addict. 28, 249–255. Ellickson, P.L., Hays, R.D., Bell, R.M., 1992. Stepping through the drug use sequence: longitudinal scalogram analysis of initiation and regular use. J. Abnorm. Psychol. 101, 441–451.

31

Ellickson, P.L., Morton, S.C., 1999. Identifying adolescents at risk for hard drug use: racial/ethnic variations. J. Adolesc. Health 25, 382– 395. Gfroerer, J.C., Wu, L.-T., Penne, M.A., 2002. Initiation of marijuana use: trends, patterns, and implications. Substance Abuse and Mental Health Services Administration, Office of Applied Studies, Rockville, MD, DHHS Publication no. SMA 02-3711, Analytic series A-17. Gfroerer, J., Wright, D., Kopstein, A., 1997. Prevalence of youth substance use: the impact of methodological differences between two national surveys. Drug Alcohol Depend. 47, 19–30. Grant, B.F., Dawson, D.A., 1998. Age of onset of drug use and its association with DSM-IV drug abuse and dependence: results from the National Longitudinal Alcohol Epidemiologic Survey. J. Subst. Abuse 10, 163–173. Grant, B.F., Stinson, F.S., Harford, T.C., 2001. Age at onset of alcohol use and DSM-IV alcohol abuse and dependence: a 12-year follow-up. J. Subst. Abuse 13, 493–504. Griffin, K.W., Botvin, G.J., Nichols, T.R., Doyle, M.M., 2003. Effectiveness of a universal drug abuse prevention approach for youth at high risk for substance use initiation. Prev. Med. 36, 1–7. Harrison, E.R., Haaga, J., Richards, T., 1993. Self-reported drug use data: what do they reveal? Am. J. Drug Alcohol Abuse 19, 423–441. Hosmer, D.W., Lemeshow, S., 2000. Applied Logistic Regression. Wiley, New York, NY. Howard, M.O., Jenson, J.M., 1999. Inhalant use among antisocial youth: prevalence and correlates. Addict. Behav. 24, 59–74. Johnson, E.O., Sch¨utz, C.G., Anthony, J.C., Ensminger, M.E., 1995. Inhalants to heroin: a prospective analysis from adolescence to adulthood. Drug Alcohol Depend. 40, 159–164. Johnston, L.D., O’Malley, P.M., Bachman, J.G., 2003. Monitoring the future national results on adolescent drug use: overview of key findings 2002. Rockville, MD, National Institute on Drug Abuse, NIH Publication no. 03-5374. Johnston, L.D., O’Malley, P.M., Bachman, J.G., Schulenberg, J.E., 2004. Monitoring the future national results on adolescent drug use: overview of key findings 2003. Rockville, MD, National Institute on Drug Abuse, NIH Publication no. 04-5506. Kandel, D.B., 2003. Does marijuana use cause the use of other drugs? JAMA 289, 482–483. Kandel, D.B., Yamaguchi, K., Chen, K., 1992. Stages of progression in drug involvement from adolescence to adulthood: further evidence for the gateway theory. J. Stud. Alcohol 53, 447–457. Kandel, D., Chen, K., Warner, L.A., Kessler, R.C., Grant, B., 1997. Prevalence and demographic correlates of symptoms of last year dependence on alcohol, nicotine, marijuana and cocaine in the U.S. population. Drug Alcohol Depend. 44, 11–29. Kessler, R.C., McGonagle, K.A., Zhao, S., Nelson, C.B., Hughes, M., Eshleman, S., Wittchen, H.U., Kendler, K.S., 1994. Lifetime and 12month prevalence of DSM-III-R psychiatric disorders in the United States: results from the National Comorbidity Survey. Arch. Gen. Psychiatry 51, 8–19. Klein, J.D., Wilson, K.M., 2002. Delivering quality care: adolescents’ discussion of health risks with their providers. J. Adolesc. Health 30, 190–195. Kozel, N., Sloboda, Z., De La Rosa, M., 1995. Epidemiology of inhalant abuse: an international perspective. National Institute on Drug Abuse, Rockville, MD, NIDA Research Monograph 148, NIH Publication no. 95-3831. Kurtzman, T.L., Otsuka, K.N., Wahl, R.A., 2001. Inhalant abuse by adolescents. J. Adolesc. Health 28, 170–180. Lynskey, M.T., Heath, A.C., Bucholz, K.K., Slutske, W.S., Madden, P.A., Nelson, E.C., Statham, D.J., Martin, N.G., 2003. Escalation of drug use in early-onset cannabis users vs co-twin controls. JAMA 289, 427–433. Needle, R., McCubbin, H., Lorence, J., Hochhauser, M., 1983. Reliability and validity of adolescent self-reported drug use in a family-based study: a methodological report. Int. J. Addict. 18, 901–912.

32

L.-T. Wu et al. / Drug and Alcohol Dependence 78 (2005) 23–32

Novins, D.K., Beals, J., Mitchell, C.M., 2001. Sequences of substance use among American Indian adolescents. J. Am. Acad. Child Adolesc. Psychiatry 40, 1168–1174. Office of Applied Studies, 2001a. Treatment Episode Data Set (TEDS): 1994–1999. National Admissions to Substance Abuse Treatment Services. Substance Abuse and Mental Health Services Administration, Rockville, MD, DHHS Publication no. SMA 01-3550, Drug and Alcohol Services Information System series S-14. Office of Applied Studies, 2001b. Summary of Findings from the 2000 National Household Survey on Drug Abuse. Substance Abuse and Mental Health Services Administration, Rockville, MD, DHHS Publication no. SMA 01-3549, NHSDA series H-13. Office of Applied Studies, 2002a. Results from the 2001 National Household Survey on Drug Abuse, vol. I. Summary of National Findings. Substance Abuse and Mental Health Services Administration, Office of Applied Studies, Rockville, MD, DHHS Publication no. SMA 023758, NHSDA series H-17. Office of Applied Studies, 2002b. Results from the 2001 National Household Survey on Drug Abuse, vol. II. Technical Appendices and Selected Data tables. Substance Abuse and Mental Health Services Administration, Office of Applied Studies, Rockville, MD, DHHS Publication no. SMA 02-3759, NHSDA series H-18. Office of Applied Studies, 2003. Results from the 2002 National Survey on Drug Use and Health: National findings. Substance Abuse and Mental Health Services Administration, Office of Applied Studies, Rockville, MD. DHHS Publication no. SMA 03-3836, NHSDA series H-22. Pagare, D., Meena, G.S., Singh, M.M., Sahu, R., 2004. Risk factors of substance use among street children from Delhi. Ind. Pediatr. 41, 221–225. Palmgreen, P., Donohew, L., Lorch, E.P., Hoyle, R.H., Stephenson, M.T., 2001. Television campaigns and adolescent marijuana use:

tests of sensation seeking targeting. Am. J. Public Health 91, 292– 296. Research Triangle Institute, 2002. SUDAAN user’s manual: Release 8.0. Research Triangle Institute, Research Triangle Park, NC. Sch¨utz, C.G., Chilcoat, H.D., Anthony, J.C., 1994. The association between sniffing inhalants and injecting drugs. Compr. Psychiatry 35, 99–105. Turner, C.F., Ku, L., Rogers, S.M., Lindberg, L.D., Pleck, J.H., Sonenstein, F.L., 1998. Adolescent sexual behavior, drug use, and violence: Increased reporting with computer survey technology. Science 280, 867–873. Turner, C.F., Lessler, J.T., Gfroerer, J.C., 1992. Survey Measurement of Drug Use: Methodological Studies. National Institute on Drug Abuse, Rockville, MD, DHHS Publication no. ADM 92-1929. Vega, W.A., Aguilar-Gaxiola, S., Andrade, L., Bijl, R., Borges, G., Caraveo-Anduaga, J.J., DeWit, D.J., Heeringa, S.G., Kessler, R.C., Kolody, B., Merikangas, K.R., Molnar, B.E., Walters, E.E., Warner, L.A., Wittchen, H.U., 2002. Prevalence and age of onset for drug use in seven international sites: results from the International Consortium of Psychiatric Epidemiology. Drug Alcohol Depend. 68, 285–297. Wagner, F.A., Anthony, J.C., 2002. From first drug use to drug dependence: developmental periods of risk for dependence upon marijuana, cocaine, and alcohol. Neuropsychopharmacology 26, 479–488. Winters, K.C., Stinchfield, R.D., Henly, G.A., Schwartz, R.H., 1990. Validity of adolescent self-report of alcohol and other drug involvement. Int. J. Addict. 25, 1379–1395. Wu, L.T., Pilowsky, D.J., Schlenger, W.E., 2004. Inhalant abuse and dependence among adolescents in the United States. J. Am. Acad. Child Adolesc. Psychiatry. 43, 1206–1214. Yamaguchi, K., Kandel, D.B., 1984. Patterns of drug use from adolescence to young adulthood: II. Sequences of progression. Am. J. Public Health 74, 668–672.